Method and structure for LED with nano-patterned substrate

A method comprising:

• forming a dielectric material layer on a sapphire substrate;
• forming a nano-mask layer on the dielectric material layer, wherein the nano-mask layer includes nano-sized grains randomly distributed on the dielectric material layer;
• performing a first etching process to remove the dielectric material layer uncovered by the nano-mask layer, forming nano-rods each including a dielectric feature from the dielectric material layer and one of the nano-sized grains overlying the dielectric feature;
• growing a first epitaxy semiconductor layer on the sapphire substrate within gaps of the nano-rods, forming a nano-composite layer having the first epitaxy semiconductor layer and the nano-rods embedded in the first epitaxy semiconductor layer;
• growing epitaxy semiconductor layers on the nano-composite layer;
• bonding another substrate to the epitaxy semiconductor layers;
• applying a radiation energy to the nano-composite layer;
• applying a mechanical force to the nano-rods to separate the sapphire substrate from the epitaxy semiconductor layers;
• and
• performing a second etching process to the epitaxy semiconductor layers, resulting in a rough surface of the epitaxy semiconductor layers.